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RadeonHD Driver Power Management Improves

Phoronix: RadeonHD Driver Power Management Improves

While we just shared that there are now patches available that introduce HDMI audio support for the xf86-video-ati driver, the RadeonHD driver has picked up improvements for power management, an area where previously the xf86-video-ati driver was in a better position. Novell's Matthias Hopf added some power management support for an area of the AtomBIOS that he had reverse engineered, after AMD hadn't provided any public documentation on the matter. With this new power management code, the xf86-video-radeonhd driver will attempt to read voltage and clock information from the AtomBIOS and then try to figure out the different combinations of voltages and frequencies that will work without leaving the card in a non-functioning state...

Realistically, both radeonhd and radeon are likely to go away eventually, assuming that both KMS and 2D/Xv acceleration over Gallium3D work out as planned.

What we think of as "full" power management (ie dynamic adjustment of clocks and voltages based on current and anticipated system workload) will probably only get implemented on top of KMS, ie in the kernel.

In the meantime, however, this level of power management work continues to be useful, and it's not a big surprise that developers experiment with new features in the code they know best. Even after KMS becomes the norm, I expect some work will still be done first in usermode drivers simply because debugging in usermode seems to be less of a pain than working in the kernel.

If you look at the commit logs, the DDX drivers have been pretty stable for the last six months, with most of the changes either related to adding new GPU support (we add the same changes to both drivers), experimenting with new features (eg this power management work), or adding compatibility with changes in other drivers (eg making the acceleration code in radeon work with KMS/GEM).

To defent radeonhd, I just switched today to radeonhd, I first tried the xf86-video-ati driver from git, it was way too problematic, I had artifacts and all such of weird behavior. I then installed radeonhd and all works very smooth and VT switching is very smooth, I am very happy with radeonhd now. Still there is a long way to go. But well, once have to wait, since AMD/ATI developers doesn't care about giving the consumers a good driver so they can use their hardware in the best enjoyable way.

Of course these drivers maybe temporary solutions. But then radeonHD had things xf86-video-ati did not have and v.v.. I personally welcome the powersaving a lot. And remember folks, it's free code so if it is suitable somehow it can be used in other drivers as well. Be it in kernel land or in a different user land driver. And powersaving is really needed on all these modern chips.
So I'm in joy reading these news.

I'm using 1.2.5 version of radeonhd. Is there a new version, or do I need to do a git pull on some repository? There doesn't seem to be a coherent location with up-to-date instructions for downloading/installing the driver so I never really know how I should be doing it, or whether any instructions I do find are current.

I'd happily use radeon instead if it gives me power management, but I can't figure out how best to install that one either.

I'm using 1.2.5 version of radeonhd. Is there a new version, or do I need to do a git pull on some repository?

The newest features will only apply to git right now.

There doesn't seem to be a coherent location with up-to-date instructions for downloading/installing the driver so I never really know how I should be doing it, or whether any instructions I do find are current.

Thanks, that looks useful. But I'm getting the impression that the power management changes are just laying the path for the future, rather than doing anything that will reduce power on my card as of now - is that correct?

I'm using Debian (testing) - although I keep thinking of switching to Ubuntu, but it always seems like a lot of effort for little discernible benefit, so I never quite get round to it.

Am I right in assuming PPAs are Ubuntu specific, or can I use them in Debian too?